Pyrroloquinoline quinone (hereinafter sometimes referred to as “PQQ”) has been proposed as a possible new vitamin (Non-patent document 1), and has attracted much attention as a useful material for dietary supplements, cosmetics, etc. Moreover, PQQ is present not only in bacteria but also in eukaryotic molds and yeasts and plays an important role as a coenzyme. Also, PQQ has been found to have many physiological activities such as cell growth-promoting activity, anti-cataract activity, hepatic disease-preventing and therapeutic activity, wound healing activity, antiallergic activity, reverse transcriptase-inhibiting activity, glyoxalase I-inhibiting activity-anticancer activity, and the like.
PQQ can be obtained by subjecting PQQ crude product obtained by methodologies such as organic chemical syntheses (Non-patent document 2) and fermentation processes (Patent document 1) to chromatography and concentrating the PQQ fraction in the effluent to crystallize PQQ by crystallization, followed by drying the crystallized PQQ (Patent document 2). The crystal structure of this PQQ salt has been reported (Non-patent document 3).
Heretofore, foods and pharmaceuticals containing PQQ have often been provided in solution or powder. Gel-like substances containing PQQ are not known. Gelled foods and pharmaceuticals, which are different in the tactile sense and handling from liquid ones, are widely used such as jellies and puddings. Moreover, use of jelly-like foods and pharmaceuticals are to be desired because they are easily swallowed even for those with impaired swallowing function (difficulty swallowing food) due to aging and diseases who find it difficult to take hard tablets. In addition to the food sector, and for cosmetics and chromatography, gel-like substances are also used for familiar goods such as athletic shoes and deodorants.
Usually, gelling agents used in the food and pharmaceutical sectors are macromolecular substances represented by collagen, hyaluronic acid, vegetable gelatin and carrageenan. Besides such macromolecular compounds, some small molecule compounds are reported to form a gel as gelling agents (Non-patent documents 4 and 5). However, no small molecule gelling agents are known that can be used for food products. Furthermore, gelling agents for use in the food sector are required to form a gel at near room temperature for preventing denaturation, although many of the macromolecular gelling agents are often formed by dissolving by warming and then cooling.